package sqlist;
import java.util.*;

public class TripList {
    public static List<Character> func(String s1,String s2){
        if(s1 == null || s2 == null){
            return null;
        }
        if(s1.length()==0 || s2.length()==0){
            return null;
        }
        List<Character> alist = new ArrayList<>();
        for (int i = 0; i < s1.length(); i++) {
            if(!s2.contains(s1.charAt(i)+"")){
                alist.add(s1.charAt(i));
            }
        }
        return alist;
    }

    public static void main(String[] args) {
        String s1 = "welcome to bit";
        String s2 = "come";
        List<Character> alist = func(s1,s2);
        for (char e: alist) {
            System.out.print(e);
        }
    }
}
